Stabilization of 1,1,1-trichloroethane

ABSTRACT

The reaction of 1,1,1-trichloroethane with metals in inhibited by the presence in the 1,1,1-trichloroethane of a small amount of benzyl fluoride and/or benzotrifluoride.

United States Patent Archer et a1.

[451 Aug. 1, 1972 [54] STABILIZATION OF 1,1,1-

TRICHLOROETHANE [72] Inventors: Wesley L. Archer, Midland; Elbert L.Simpson, Auburn, both of Mich.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Sept. 21, 1970 [21] Appl. No.: 74,154

[52] US. Cl ..260/652.5 R, 252/162, 252/171 [51] Int. Cl. ..C07c 17/42,C070 17/40 [58] Field of Search ..260/652.5; 252/162, 171

[56] I References Cited UNITED STATES PATENTS 3,049,571 8/1962 Brown..260/652.5

Primary Examiner-Howard T. Mars Att0rneyGriswold & .Burdick, J. RogerLochhead and Glwynn R. Baker a 7] ABSTRACT The reaction of1,1,1-trichloroethane with metals in inhibited by the presence in the1,1,1-trichloroethane of a small amount of benzyl fluoride and/orbenzotrifluoride.

1 Claim, No Drawings STABILIZATION OF 1 1 l -TRICHLOROETHANE BACKGROUNDOF THE INVENTION This invention relates to the stabilization ofchlorinated solvents. More particularly, the present invention concernsthe stabilization of 1,1,1- trichloroethane in the presence of metals,such as aluminum, iron, brass, zinc and the like.

Chlorinated hydrocarbons such as trichloroethylene and perchloroethyleneare commonly used as solvents in chemical processes, dry cleaning, andmetal degreasing. Solvents of this type are subject to slowdecomposition and oxidation reactions, particularly in the presence ofimpurities such as water, traces of acid or metal salts. Corrosion ofmetal surfaces in containers and process equipment and deterioration ofsolvent quality by formation of acidic and colored byproducts therebybecome serious problems. Inhibitors such as acid scavengers andantioxidants are commonly added to these solvents in order to preventsuch degradative reactions. Inhibitor concentrations are normally of theorder of one percent by weight or less.

1,1,1-Trichloroethane poses a particularly difficult stabilizationproblem because of its unusual reactivity with the above metals, notablyaluminum. Traces of metal salts, moisture or other impurities are notneeded to initiate the 1,1,l-trichloroethane-aluminum reaction, for thisreaction occurs spontaneously on a freshly exposed aluminum surface withspectacular results, converting the solvent and the metal surface in afew minutes to a blackened mass of acidic, carbonaceous material andaluminum salts. Conventional acid acceptor stabilizers cannot bedepended upon to inhibit the aluminum-l,1,1-trichloroethane reaction andsuitable inhibitors must be discovered by independent investigation. Thesearch has yielded few effective compounds and these show little or noobvious pattern of structure. Typical 1,1,1-trichloroethane formulationscontain about 5 percent by weight of inhibitor which is usually acombination of compounds to inhibit reaction of the solvent with avariety of metals.

SUMMARY OF THE INVENTION It has now been found that the1,1,l-trichloroethane tion of metals and 1,1,1-trichloroethane need beused. Although any significant amount will provide some inhibition,preferably about 0.1 to 1.0 gram mole per liter of 1,1,1-trichloroethaneis employed.

SPECIFIC EMBODIMENTS The above compounds were tested forinhibitingactivity in elongated glass test tubes having an inside diameter of 0.8cm. and 33 cm. in length. To each vertically disposed tube there wasadded 0.54 g. of essentially pure 16-32 mesh granular aluminum and asolution of the inhibitor in purified 1,1,1-trichloroethane to makeatotal volume of test ixture of 5 The c1 se en s o the test tubes were ten immerse in an 011 at held at a temperature sufficient to maintain the1,1,1- trichloroethane solution in each tube at a steady reflux. Theresults listed in the following examples indicate the minimumconcentration of the inhibitor found effective to provide completeinhibition of the 1,1,1- trichloroethane-aluminum reaction for 24 hoursunder these conditions. Prevention of the reaction for this length oftime under the described conditions indicates capacity for effectiveinhibition for an indefiniteperiod. Concentrations are given in grammoles per liter. this figure being convertible to weight percent by theequation (moles/liter) (mol. wt. of inhibitotl' Wt. percent 13.46 7

Effective Concentration Example Compound g.-moles/liter 1 benzylfluoride 0.017 2 benzotrlfluorlde 0.50

Additional tests, utilizing 2 l inch X l inch X 1/l6 rosion ratings arerepresented by numbers 0-5, where 0 is no corrosion up to 5 which isheavy corrosion.

Condition of coupons 2024 A1 1100 Al Iron Brass Zinc Fluoro compoundL.1. VJ. 11.1. v.1. 11.1 v.1 L.l v.1 11.1. yr. Color of [lnul soln.

Bcnzyl lluoridc l) U 0 0 0 0 0 1 .2 0 'lurbid but colorless.Benzotrilluoritle l) 0 t) 0 0 U 1 1 1 t) Colorless.

L.l. are liquid phase corrosion observations. -V.1. are vapor phasecorrosion observations.

reaction can be substantially retarded or prevented by We claim:

incorporating into the 1,1,1-trichloroethane an inhibit ing amount ofbenzyl fluoride or benzotrifluoride. Such compounds may be used alone orin combination with each other or with other nonreactive conventionalinhibitors, such as nitromethane and an epoxide.

Only a quantity of benzyl fluoride and/or benzotrifluoride sufficient toretard or to stop the reac- 1. A 1,1,1-Trichloroethane compositionstabilized against reaction with metals consisting essentially of

